We experienced one case of the coronary artery aneurysm. The patient was 67 years old female, who complained of dyspnea on exercise[NYHA functional class III] for two years. Coronary angiogram demonstrated a localized saccular aneurysm on left main coronary artery, just above bifurcation of left anterior descending coronary artery and circumflex artery. On the operative field, the aneurysm was 2cmx2cmx 1.5cm in size with 0.5cm in neck. Resection and aneurysmorrhaphy was done. The patient was recovered and discharged uneventfully. During 8 months follow-up period, she lives in good physical activity and absence of chest pain.